Opening LR4.x catalog with LR5.x, without conversion

Question

Here's the problem: I need to open backup catalogs that had been saved with older versions of LR, using my current 5.6 version so I can search for some work that is missing.  Once I find it, I can export those photos and work to a small catalog and then import it into my current 5.6 catalog.  However the problem is older catalogs cannot be opened with newer versions of LR.  The first thing LR wants to do, is convert the catalog and update all the previews.  I would have to hide my current 5.6 catalog and previews o they won't be overwritten and wait for all that conversion to occur, for each backup I need to take a peek inside.
Is there a quicker way to view older catalogs to see if specific work and photos are in there, without having to update them first?
(BTW, the problem I have is I'm missing two entire years of photos, probably because LR was using the wrong catalog from the 4.2, 4.3, 4.4, etc versions that had accumulated, so not everything was being kept in one catalog).
Andy

Answer 1

Here's what I've found so far.
Multiple versions can be installed at the same time (and I assume will operate independently though I wouldn't go so far as running more than one at a time).  However you have to install them in descending order.  If 4.3 is installed, then 4.4 it will first delete 4.3.  So Install 4.4 first, then 4.3.
Next, is which catalog they open.  By default the Windows registry just says "Lightroom" opens the lrcat file, and isn't specific whether it's the LR from the \Lightroom 4.3 directory, or the \Lightroom 4.4 directory, etc.  It's also not possible to rightclick the lrcat file and pick Open With, since the versions of LR are not listed individually.
The next bit is just for information since I don`t think this completely solves how to have LR start with a specific cat file.
There is an agprefs file in \Users\username\AppData\Roaming\Adobe\Lightroom\Preferences\  This is just a text file, so use Notepad to edit this.  Near the end is the variable named "libraryToLoad20".  Change the text string to name the catalog to be opened, such as Lightroom 4o3 Catalog.lrcat or Lightroom 4o4.lrcat.  Don't use a period in the LR version, that might confuse something.  As long as the agprefs file is edited first, LR will open the catalog you intend when it starts.  I prefer to do this, rather than let it open an inappropriate catalog and then pick Open Catalog after it's started.  The problem with this approach, is LR will then create a subdirectory Lightroom 4o3 Catalog Previews.lrdata if it doesn`t exist yet.  So although it`s interesting the agprefs file can be ``hacked`` to control which catalog LR starts with, I think I`ll just let it open and then use File, Open Catalog.  The only problem may be whether the old backup lrcat file I open, names a specific Previews directory and by now it`s name has changed!